1. Field of the Invention
The present invention relates generally to ceramics manufacture and more particularly to sintering aid compositions used in preparing ceramic articles.
2. Background of the Invention
Sintering is the action of fusing of inorganic powders at high temperature to produce a ceramic article or part. Often sintering is also termed “firing.” In ceramics, this firing or sintering is often done in a high temperature furnace or the like. An example of a ceramic material formed in this way is silicon carbide (SiC), which is composed of uniformly-sized SiC powder and which is fired to form the ceramic. At the microscopic level, a piece of SiC ceramic is composed of a three dimensional ordered array of uniformly-sized SiC spheres (<1 micron in diameter) which are fused at their edges. The strength of the SiC ceramic comes from the uniformity of its ordered array.
Inorganic powders, such as SiC, typically have very high melting points. Sintering aid compositions act to reduce the melting point of the SiC so that the material can fuse at a lower (and more achievable) temperature. A drawback of using sintering aid compositions is that sintering aid materials remain in the ceramic article after the firing process. Traditional sintering aid compositions have used fine powders containing boron and carbon. These materials disrupt the ordered array of SiC spheres weakening the strength of the ceramic piece. These disruptions of the ordered arrays are points of failure when the ceramic is stressed.